The present invention relates generally to combine harvesters and, more particularly, to improvements in the cleaning apparatus to permit a leveling thereof under sidehill conditions.
The operation of combine harvesters under sidehill conditions, i.e., a lateral inclination of the combine in a non-horizontal position, is less efficient than the operation of the combine operating on generally level ground because of the gravity induced movement of threshed grain to the downhill side of the cleaning apparatus. This unbalanced loading of the cleaning mechanism prevents a proper flow of air from a cleaning fan through the threshed grain to facilitate the removal of chaff and other debris.
This unbalanced lateral distribution of material across the cleaning mechanism reduces or eliminates the aerodynamic separtaion and cleaning of the threshed grain by the flow of air through the sieves. As a result, the cleaning mechanism delivers a greater amount of uncleaned grain to the returns system for reprocessing and also discharged out the rear of the combine to be lost from the harvesting process. One known method of eliminating this problem is to reduce crop intake; however, operating efficiency of the combine is correspndingly reduced which is not desirable.
One attempt to maintain a combine cleaning apparatus in a horizontal orientation while the combine is operating under sidehill conditions is found in U.S. Pat. No. 3,731,470. With this particular apparatus, the entire frame of the combine is leveled through the operation of hydraulic cylinders, requiring a modified connection of the crop harvesting header to the combine to permit a proper gathering of the crop material to be harvested. Another cleaning apparatus leveling mechanism can be seen in U.S. Pat. No. 4,344,443, which provides that the entire cleaning mechanism, including the fan, is pivotally mounted for movement relative to the main frame about a longitudinally extending pivotal axis. However, this particular mechanism is expensive to manufacture, is cumbersome in operation, results in an unnecessary shifting of major structural components and requires a more complex main frame structure and drive train components.